Experimental Study On The Combustion Characteristics Of Low Volatile Pulverized Coal Blended With Biomass

Biomass is a kind of high volatile content of renewable energy and low volatile pulverized coal is a kind of low volatile content which is not easy to light energy. Co-combustion of biomass and coal can improve the volatile content of the fuel, reduce the ignition point of the mixed fuel, reduce pollutants (NOx, SOx) and CO2 emissions and promote the rational use of biomass fuels.It is a kind of low-cost,low-risk renewable utilization way.In this paper, corn stalks, sorghum stalks, soybean straw, apple tree branches, sweet potato vines five kinds of biomass and low volatile pulverized coal are used as fuel. It has maken experiments of the TGA tests and emission tests under both environments of coal co-firing and single firing.It also analyses these characteristics of the combustion and emissions of pollutants under different conditions and the dynamics under the basis of thermogravimetric experiment.Then it determines the kinetic parameters and calculates the combustion characteristic index.In thermogravimetric experiment, DTG curve of biomass burning and low volatile coal combustion is a single peak. As biomass mixing ratio increasing, TG curve has a tendency of moving to the left side of the low temperature range,at the same time the volatile peak will become larger and wider and the eke peak will become smaller and more narrow and the ignition temperature will decrease significantly. And with the increase of particle size, the TG curve has a tendency of moving to high temperature area. The DTG curves of mixed 120 mesh sorghum straw corresponding to the volatile combustion peak is the largest, and its characteristic parameter value is smallest.With the increasing of heating rate,the TG curve shifts to the right temperature zone, and these two peaks of DTG curves will become larger and the peak width will become more narrow while the combustion characteristic parameter increases,at the same time the increasing tendency ofthe ignition temperature will become slighter. In short, blending biomass can promote coal combustion and reduce the ignition temperature and increase the degree of burn and improve combustion characteristics.Biomass activation energy which can be obtained from the dynamics analysis is between 20kJ/mol to 30 kJ/mol while low volatile coal is greater than the activation energy of biomass. Co-combustion of biomass and low volatile coal can reduce the activation energy especially the activation energy of mixing apple tree branch. With the increase of biomass mixing ratio, co-combustion activation energy will become more and more small. Particle size blended biomass for co-firing have an impact on the activation energy,in which 120 mesh sorghum corresponding activation energy is minimized. Under different heating rate of soybean straw and coal co-combustion, the activation energy has different size.When biomass and low volatile coal are burned in a single linear fitting correlation coefficient of 0.95 or more, when co-firing correlation coefficient were 0.97, so biomass and coal co-firing’s linear fit better. And with the increase of biomass mixing proportion and heating rate, combustible, ignition and combustion characteristic indexes showed a trend of increase gradually.In the tube furnace experiment,the biomass and low volatile pulverized coal which is burnt in single or mixed pollutants instantaneous emission curve exists an obvious peak. Different biomass and low volatile coal co-combustion pollutants emission curves are similar, which blended apple tree branch in the early combustion and it is more rapid.The NO and SO2 emission peak of the curve is also the largest. As corn stover mixing ratio increase from 10% to 30%, NO and SO2 emissions curve has obvious downward trend and the range of emissions will become more narrow and emission peak is also getting smaller and smaller. At the same time, the temperature is higher,the NO concentration value is greater and the curve peak is also growing. The temperature is higher, the pre-mixture combustion SO2 emission value is greater.The temperature is higher, the SO2 emission value in the early stage of the mixture combustion is greater and precipitate is sooner and the SO2 emission peak of the curve is greater.